Direct Evidence from Gas-Phase Atomic Spectra for an Unscreened Intra-Atomic Origin of Outer-Core Multiplet Splittings in Solid Manganese Compounds

We compare for the first time gas-phase $3s$ and $3p$ spectra from atomic Mn with corresponding spectra from the solid compounds MnF₂ and MnO. These spectra are found to be strikingly similar, indicating that the solid-state spectra have a dominant origin in unscreened intra-atomic multiplet splittings, perhaps with correlation-induced satellites. Such outer-core hole states are thus not describable in terms of a simple superposition of fully screened and poorly screened spectra as recently proposed.